The present invention relates in general to a therapeutic device for the administration of a medicament or active agent to a host upon adhesion thereto by an adhesive layer. More particularly, the therapeutic device allows for topical or systemic administration to the host, or administration through the skin or mucosa of the host over a period of time, while isolating the medicament or active agent contained within a reservoir from the adhesive layer during storage and administration of the medicament or active agent to prevent the contamination of the active agent, to prevent deterioration of the adhesive and to avoid trapping of the drug within the device itself.
Transdermal administration system are known in the art. For example, Ciba-Geigy's Transderm.RTM.-Nitro and Transderm.RTM.-V systems have been approved for transdermal administration of nitroglycerin and scopolaimine, respectively. Similar such devices are also described, for example, in U.S. Pat. Nos. 4,460,368, 4,460,370, 4,460,372, 4,379,454, 4,486,194 and 3,972,995.
Characteristically, those controlled continuous transdermal devices known before the present invention contained a backing member which defined the outer surface of the device, a membrane sealed to the backing member to create a reservoir therebetween containingg the active agent, and an active agent permeable adhesive layer on the membrane defining the other face. Alternatively, the active agent, rather than being in one separate reservoir, is contained in a plurality of microcapsules distributed throughout the permeable adhesive layer. In either case, the active agent is delivered continuously from the reservoir or microcapsules through the membrane into the active agent permeable adhesive, which contacts the skin or mucosa of the recipient. Thus, in such devices, substantially the entire face, or surface, in contact with the skin or mucosa consists of the active agent permeable adhesive through which the active agent is administered. While such devices have a number of advantages, including full contact to the skin, certain potential disadvantages are apparent therewith.
For example, unless due care is exercised, contamination of the permeable adhesive layer can easily occur by finger contact when a user applies the device to the skin. Thus, where the fingers are sufficiently contaminated with perspiration, body oils and foreign matter, the resulting contamination of the permeable adhesive layer may adversely affect its permeable nature and cause a deterioration of its adhesive nature. This can also adversely affect the desired predetermined rate of transport of the active agent to the recipient, loss of its effecitveness, and can potentially cause infection to occur. Moreover, finger contact with the permeable adhesive layer will contaminate the finger with the active agent. This is undesirable, for example, where the active agent is an eye irritant such as scopolamine, subsequent contact of the contaminated finger to the eye may result in irritation.
In addition, contact between the adhesive layer and the active agent can also result in contamination of the active agent itself, with obvious deleterious effects, including loss of its effectiveness and the potential to cause infection or other such adverse effects upon the recipient. Furthermore, the construction of the known devices generally maintain the permeable adhesive layer in contact with the active agent contained within the reservoir during storage of the device from the time of its manufacture. Thus, there is a need for the permeable adhesive layer to be formulated specifically to match the drug or active agent, i.e., so that it will permit the drug to pass therethrough without trapping the drug, or becoming a "sink" therefor.